Category: projects

I’ve been trying to maintain a rule that things thrown away at work do not come home with me, especially if they don’t have an immediate use. This week it failed me. We had bought an IoT printer kit from adafruit ages ago as an early part of a project idea, but it was never assembled or came to fruition. As a result it’s been sitting on the shelf for about 3 years untouched. Since we are cleaning out old stuff from the lab, it ended up being placed on the junk cart. Normally, I’d be happy to let something like this go, but it had lots of neat parts and bits in it. I even came up with a project idea in the next day! I’m going to try to make a shopping/generic list printer, powered by mono on the printer, and my pebble watch for input. I also […]

The day has finally arrived! Sparkfun had a dumpster dive last week, and I managed to get a 0.5lb box. I had the big box in my cart too, but it was out of stock before I could get to checkout. With some knolling: And now for the list of goodies: FTDI 5V cable 9V battery holder with barrel jack 56 and 200K resistors 10K pot with wires 4 matching pot knobs VGA connector Lilypad Arduino v1.1 (works so far) 5pk of lilypad green LEDs. 12pk of some 12A 60V P-Channel MOSFETs (NTD2955) 3V coin cell some kind of snapping connectors for fabric (Female half) A slightly mangled breadboard A base for a breadboard and some Dev board. some screws (hopefully M3 but might be #4-40) some Brass standoffs (hopefully M3 but might be #4-40) some small female headers (mostly 1×4) An enclosure with some milled holes (happens to be […]

This is part 2 of the led grid project, a joint project of engunneer.com and ericagunn.com. In the last post, the boards had just arrived, and the rest of the parts were on order. A few days later, everything was here! Because resistors are so cheap when you get 100 or 500, it was worth getting a few extra values to allow for testing the IR receivers. Just before assembly, I realized why DirtyPCBs are so cheap, and why they do electrical tests on all boards: Yes, that’s blue sharpie on top of a hand repaired trace. About 30% of the boards had some kind of repair like this. I soldered one board up and started testing. Getting the color LEDs working wasn’t a big deal, but I had problems with the IR power supply (which is also duplicated for the shift registers). It just wasn’t regulating voltage and had […]

This is a copy of a guest post I wrote for my wife’s blog, about building an LED Grid for our collaborative design project The hardware for the LED grid project consists of two major elements: The LED lights, and the IR touch system. The first idea for the board had the main LEDs spaced out in a 10mm grid. I prototyped this on some surface mount prototyping board to see if I could fit everything needed into the space available. It was a bit of a tight fit, and the nature of how I made it makes it not very pretty. Because the LED cells were so close together, I had to alternate the IR touch transmitters and receivers in each column to keep them from interfering with each other. This was enough to prove out the concept and get initial values for the resistors for the touch system. […]

3D printing as a hobby brings with it plenty of tinkering. I noticed an effect in my printed parts that looks like z wobble from my old cupcake, but the openbeam printer should be better constrained in the xy axes to prevent that. Basically there are 8mm guide shafts that keep everything aligned and a pair of z motors with misalignment couplings and a threaded rod and M8 nut to actually impart the force in the z direction with minimal x and you components. I had used some spare M8 threaded rods that I bought from makerbot when they were clearing out old cupcake parts. What I noticed was that the ridges on my parts changed size as a function of layer height. This meant that some layers were being squished more than others. The pattern was the exact same pitch as the threaded rod, which meant the z didn’t […]

Disclaimer: I am NOT a web programmer, nor am I a PHP expert. In preparation for FRC season, I decided to do some maintenance of the quiz website where I have hosted FRC rules quizzes for the past two years. Apparently Webtester has two(or more) major security holes. I discovered at least 12 different malicious files uploaded, and at least two other major problems on my site. I’m going to document here what I did to fix my copy of Webtester (version 5.1.20101016), since I haven’t really found a better tool for the way I want to host quizzes. I’m taking two approaches to this: Closing known holes (Google for “WebTester 5.x Multiple Vulnerabilities” to see a few detailed reports), and obfuscating obvious things. At least one of the attacks made an attempt at getting the details of any blog software I use, but I think the randomized table prefix […]

There was a discussion on the askelectronics subreddit about part storage, which reminded me that I’ve been meaning to post about the latest office arrangement. For the video tour, see this post. Since the main question is about components, I’ll start there. Since the organization has grown over a decade or so, there is some duplication and some things that could be grouped better, which is an ongoing process. This is the main electronics workbench in my office: From top row, left to bottom row right: Grey bins – the oldest bins. Contains US machine screws, wood screws, nails, etc. Teal bins – until recently this was metric hardware and rivets, but most of that has moved to primary storage (covered below) – now mostly empty Partitioned containers. These are $10 from the container store. There are 5 in use here and 3 more emptys in primary storage. This is […]

Problem: Running my makerbot over serial can be problematic because I have an aged laptop. I’m still using an old laptop I scavenged when IT was giving away tired machines. It has a Core 2 Duo at 2Ghz, a 40GB hard drive and 3GB RAM (32 bit OS). It’s still kicking, and can usually do what I need without too much hassle. Recently though, The act of switching windows during a print caused the serial buffer to run out, and the printer would sit for 30 seconds oozing while it waited for more data. Solution: Enter OctoPrint. I recently got a Raspberry Pi model B for a larger PCB design project I was planning, but that is temporarily on hold. I did some reading about what I could do with it, and was torn between a pandora interface for the stereo downstairs, and a mini-host for the 3D printer. Once […]

With the TDS544A up and running, I decided to take a crack at getting data off of it. The scope has a floppy drive (but my laptop doesn’t), a GPIB port, and a printer card with both parallel and serial interfaces. The hardcopy menu has around 18 options for filetypes, and is capable of sending the screenshot to any of the ports or the floppy drive. Of the options available, I decided to try sending a windows BMP file over the serial port. I used a F-F null modem cable and a USB to Serial converter. On the program side, I started with this autohotkey script which spews data from your serial port into notepad. With a little bit of munging (removing anything to do with sending data, and removing some of the ASCII conversion logic), I was able to get and write BMP files. A full 640×480 color bitmap […]